This invention pertains to a novel pressure relief disc assembly which is useful as a safety valve when it is in operative communication with a positive displacement pump.
Positive displacement pumps are widly used items of commerce. Such pumps have a power source driving at least one piston (and usually an odd number of pistons) in a reciprocating path within the confines of a cylinder. The piston(s) usually are connected to the power source by way of a crankshaft or camchaft. In opeation, the reciprocating piston in a positive displacement pump alternately creates a vacuum (on the backstroke) and a pressure (on the forward stroke) within the cylinder and any chamber in fluid communication with the cylinder. This principle is utilized to draw fluids into the cylinder chamber through an inlet port while the piston makes its back stroke by suction (vacuum) and to discharge the fluids from the cylinder chamber through an outlet port while the piston makes its forward stroke by pressure. The flow of fluids through the inlet and outlet ports are usually controlled by operation of certain valves movably seated in each of these ports, which are pressure actuated. If the positive displacement pump has more than one cylinder, then the movement of the reciprocating pistons are usually timed by operation of the camshaft or crankshaft so as to provide a uniform flow of fluids through the pump at a substantially constant pressure.
Usually the fluid pulled into the positive displacement pump is from a common fluid reservoir located on the "suction side" of the pump. Likewise, the fluid discharged is usually discharged into a common reservoir or conduit located on the "discharge side" or "pressure side" of the pump.
Positive displacement pumps are quite efficient and operate essentially trouble-free in most instances. However, a severe safety problem can (and does) occur when the fluid is discharged from the pump into a closed vessel or conduit. This occurs, for example, when the fluid is pumped against a closed valve in the conduit. In such instance, the pressure build-up is dramatic and can result in a catastrophic rupture of the pump, the conduit, and/or the receiving vessel. Others have attempted to alleviate this problem by placing pressure sensitive "pop valves" and the like on the conduit or vessel and external to the workings of the pump. While such pop valves may be effective to prevent rupture of the system, they pose another safety problem when the release. Namely, a stream of pressurized fluid is released to the surroundings through the ruptured pop valve which can cause injury to personnel in the surrounding area.
Accordingly, a need exists for a new type of pressure relief device for use in communication with a positive displacement pump that can effectively protect personnel and equipment when the pressure side of the pump system is closed or blocked. Such a device has now been discovered.